Naslund and O'Donnell 



Chapter 12 



Daily Patterns of Activity at Inland Sites 



carrying fish and are generally silent when visiting or flying 

 around nests during the evening and are thus less easily 

 detected (Naslund 1993a, unpubl. data). 



Activity levels relative to sunrise are notably earlier at 

 northern latitudes (i.e., British Columbia and Alaska) than at 

 more southern latitudes. This difference in activity periods 

 results from differing light regimes. Pre-dawn light levels 

 are greater and occur earlier, relative to sunrise, in Alaska. 

 In this region, the seasonal variation in timing of first murrelet 

 detections appeared to track changes in light levels. Murrelets 

 were heard earliest, and occasionally throughout the "night", 

 around the summer solstice when light levels were greatest 

 (Kuletz and others 1994c). As summer advanced and light 

 levels decreased, murrelet activity occurred increasingly later. 

 Similarly, early activity in Washington and British Columbia 

 is thought to result from longer twilight periods (Eisenhawer 

 and Reimchen 1990; Hamer and Cummins 1990; Rodway 

 and others 1991, 1993b). 



Cloudy or foggy weather results in lower light levels than 

 clear mornings and may thus be affecting the timing of murrelet 

 activity similar to changes in twilight regimes. In addition, 

 murrelets may respond to periods of low fog or clouds, light 

 rain, or snow by flying lower and calling more frequently and 

 are thus detected more frequently under these conditions. 

 However, on at least some occasions, murrelets fly above the 

 fog, then drop below the fog just before entering the forest 

 canopy (Kristan, pers. comm.). The influence of weather on 

 murrelet activity is further evidenced by observations of 

 murrelets exchanging incubation duties later on cloudy mornings 

 and mornings with low cloud ceilings than on clear mornings, 

 as well as changes in behaviors at nests with changes in 

 weather conditions (Naslund 1993a, Nelson and Peck, in press). 



Although weather conditions apparently affect many 

 aspects of murrelet activity, murrelets exhibit variable 

 responses to conditions observed inland. This variability 

 may reflect differences between weather conditions at survey 

 sites and conditions that murrelets respond to down drainages 

 and other flight corridors, or at the coast. Timing and 

 duration of activity inland also reflects seasonal variation 

 in environmental conditions. For example, activity is earlier 

 and shorter in winter when days are shorter and 

 environmental conditions more extreme than in summer. 

 This presumably reduces the time available to murrelets for 

 foraging, and may increase the effort required to obtain 

 food. Consequently, less time and energy may be available 

 for inland flights. Differences may also correspond to changes 

 in social behavior or reduced numbers of birds in winter 

 (see Naslund 1993a,b; O'Donnell and others, this volume). 

 The late and reduced duration of activity observed in August 

 corresponds to a time when detections become sporadic 

 and decrease overall (Kuletz and others 1994c, Naslund 

 1993a, Nelson and Hardin 1993a). 



Temporal variation in behavior, group size, and 

 vocalization patterns of murrelets during the morning activity 

 period reflects features of nesting biology. The early timing 

 of single birds and birds flying below canopy coincides with 

 the typical times that murrelets exchange incubation duties 



and display around nest sites (Naslund 1993a; Nelson and 

 Hamer, this volume a; Nelson and Peck, in press; Singer and 

 others 1991, 1992). Similarly, murrelets make single calls 

 and wing sounds early in the morning. These behaviors have 

 also been associated with incubation exchanges, chick 

 feedings, and possible displays in nesting territories (Naslund 

 1993a; Naslund and Hamer 1994; Nelson and Hamer, this 

 volume a; Nelson and Hardin 1993a). Conversely, the larger 

 and more vocal groups that are more frequent later in the 

 morning may represent murrelets engaged in social 

 interactions or joining together for flights to sea. 



Survey Implications 



Based on the daily activity patterns described here for 

 murrelets, it is clear that current guidelines, which recommend 

 that surveys be conducted during the dawn activity period, 

 will provide the most consistent information on use of inland 

 habitat by nesting murrelets (see Ralph and others 1993, 1994). 

 Evening surveys may furnish additional information useful 

 for interpreting stand-use or furthering our understanding of 

 murrelet biology. It is evident that survey start-times should 

 be shifted earlier as one moves north to compensate for changes 

 in light levels relative to sunrise. Exact timing for some areas 

 (e.g., southwest Alaska) may require further evaluation. 



It is difficult to standardize surveys in a manner which 

 eliminates the contribution of weather conditions to daily 

 variation in activity patterns. Variability in activity is further 

 confounded by the effects of weather conditions on the ability 

 to detect murrelets. For example, fog and rain may reduce 

 observers' abilities to see or hear murrelets. However, Rodway 

 and others (1993b) found no evidence that some weather 

 conditions (e.g., cloud cover) affect the proportion of detections 

 that are seen. Avoiding surveys during certain conditions 

 (e.g., heavy rain), as recommended by current guidelines 

 (Ralph and others 1993, 1994), will reduce variation in recorded 

 activity due to differences in visibility. This can be particularly 

 important when evaluating subcanopy behaviors, which relies 

 primarily on the visual detection of murrelets. In Alaska, 

 where inclement weather prevails, surveys may be conducted 

 on all days except those with high winds and extreme rain. 

 Weather effects should be considered accordingly when 

 making temporal and spatial comparisons between surveys. 



Collection of data on group size, behaviors, and 

 vocalizations during surveys provides information that is 

 important for interpreting stand-use by murrelets. These 

 data may also prove useful for unraveling various aspects of 

 the ecology of this enigmatic species. 



Acknowledgments 



We thank Kathy Kuletz, Peter Walsh, and Michael 

 Westphal for generously allowing us access to their 

 unpublished data. This manuscript was greatly improved by 

 the insightful comments of Jim Baldwin, Alan Burger, Peter 

 Connors, David Forma, Anne Harfenist, Gary Kaiser, Debbie 

 Kristan, S. Kim Nelson, Peter Paton, John Piatt, Michael 

 Rodway, Jean-Pierre Savard, and Fred Sharpe. 



134 



USDA Forest Service Gen. Tech. Rep. PSW-152. 1995. 



